Polyester filaments for fur-like fabrics

ABSTRACT

Polyester filaments of 2 to 14 denier per filament having oblong cross sections of shapes illustrated are particularly useful in pile fabrics for providing fur-like aesthetics. In comparison with previous polyester fibers, the new fibers provide an improved smooth, non-tacky, resilient hand and pleasing luster, with freedom from fibrillation during processing or use of the fabric.

Gorrafa Oct. 21, 1975 POLYESTER FILAMENTS FOR FUR-LIKE FABRICS 75 Inventor: Adly Abdel-Moniem Gorrafa,

Hockessin, Del.

[73] Assignee: E. I. Du Pont de Nemours & Co.,

Wilmington, Del.

[22] Filed: Sept. 24, 1973 [21] Appl. No.: 400,037

{52] US. CL, 428/397; 15/159 A; 264/177 F 3,239,865 3/1966 Munt 264/177 F 3,249,669 5/1966 Jamieson 3,344,457 10/1967 Grobert 3,351,205 11/1967' Butler et a1 264/177 F 3,470,685 10/1969 Hall 264/177 F FOREIGN PATENTS OR APPLICATIONS 669,246 10/1964 Italy 264/177 F 71,385 4/1942 Czechoslovakia 161/177 41-17694 10/1966 Japan 42-5250 3/1967 Japan 264/177 F Primary Examiner-George F. Lesmes 51 Int. Cl D02g 3/00 {58] Field of Search 15/159 A; 264/177 F;

161/177, 179, 180, 62 [5 ABSTRACT Polyester filaments of 2 to 14 denier per filament hav- References C'ted ing oblong cross sections of shapes illustrated are par- UNITED STATES PATENTS ticularly useful in pile fabrics for providing fur-like 2,149,425 3/1939 Draemann 15/159 A aesthetics- In comparison with Previous Polyester 2,831,748 4/1958 Finlagson 264/177 F bars, the new fibers provide an improved smooth, non- 3,l09,220 11 1963 McKinney et a1. 15/ 159 A tacky, resilient'hand and pleasing luster, with freedom 3,156,607 11/1964 Strackan 161/177 from fibrillation during processing or use of the fabric. 3,219,739 11/1965 Breen et al..... 3,238,553 3/1966 Bailey et a1. 15/159 A l Clalm, 6 Drawlng Flgures r 2 X B i o U.S. Patent Oct. 21, 1975 3,914,488

FIG-

2 r /x d FI6.Z FIG"? FIG.4

FIG.5

FIG.6

POLYESTER FILAMENTS FOR FUR-LIKE FABRICS BACKGROUND OF THE INVENTION Pile fabrics resembling furs'have in recent years been manufactured from synthetic organic polymeric fibers and widely sold for use in garments. These pile fabrics have been used both as liners for garments or as the actual outside surface of the garment. The pile fibers have usually been acrylics, modacrylics, polyamides or polypropylene. In general, polyesters have been missing from this list because of problems relating to aesthetics. In particular, these fibers tend to develop a tacky hand when exposed to stock dyeing unless special precuations are taken. It has been found that the tacky quality results from a polyester trimer which exudesfrom the fiber during processing. The trimer and other low molecular weight materials may be removed by careful treatments, but this entails additional expense in fabric manufacture.

The objective of the present invention isto provide a polyester filament for use in fur-like fabrics having (I) a smooth, non-tacky hand, (2) pleasing luster, (3) low bending stiffness compared to round fibers, (4) good resilience in the pile, and (5) freedom from fibril lation propensity. 7

SUMMARY OF THE INVENTION The invention provides a polyester filament having a denier per filament from 2 to 14 and an oblong filament cross-section continuously along its length. The filament cross-section is characterized by major and minor axes of symmetry which are perpendicular to each other, by a ratio of length to width measured along the axes of from 1.4 to 2.4, by a lobe located on each extremityof the major axis which has a tip radius ratio r /R of 0.20 to 0.45, where r is the radius of the lobe tip and R is the radius of a circle circumscribed about the oblong section, by 'a lobe located on each extremity of the minor axis which has a tip radius ratio r /R of 0.8 to 2.1 times the tip radius ratio of the lobes on the major axis, and by indentations between the lobes, the shortest distance d between two of the indentations on opposite sides of the major axis being from 1.2 to 2.0 times the radius r, of the lobes on the major axis.

LIST OF FIGURES FIG. 1 is a diagram illustrating the method'for measuring the various filament cross-section parameters.

FIGS. 2-4 illustrate cross-sections for several filament shapes'within the scope of the inventon. The black dots on these cross-sections indicate approximate centers of curvatures for various parameters which will bedescribed in'detail.

FIG. 5 is a plan view of a cluster of three adjacent spinneret orifices used for making a single filament according to Example I. FIG. 6 is a plan view of a cluster of three adjacent spinneret orifices used for making a single filament according to Example II;

DETAILS OF THE INVENTION.

Considering FIG. 1, the cross-sectional configuration of fibers within the invention may be determined from a photomicrograph of the fiber cross-section. The length of cross-section along the major axis X is indicated by A. The widthof the cross-section along the minor axis Y is indicated by B. The ratio of length to width of the cross-section is A/B.

' In the melt-spinning of filaments, the polymer tends to flow so as to produce smooth curves or combinations of smooth curves and straight lines in the periphery of the cross-section. For the purpose of measurement, the periphery may be considered to be composed of straight'lines and arcs of circles. Using this concept, filaments of the invention have a lobe located at each end of the major cross-sectional axis, the extreme portion of the lobe being an arc of a circle. The radius of this lobe tip is indicated by r at each end. Likewise, a lobe is located at each end of the minor axis Y of the crosssection; the radius for each lobe tip being indicated by r While FIG. 1 shows the center of curvature for both lobes at the same point on the minor axis, this is not essential. The centers of curvature for the lobes on the minor axis may be separated, for example, as in FIGS. 2 to 4. The circumscribing radius for the cross-section is indicated by R. The tip radius ratio for the lobes on the major axis is r /R and for the lobes on the minor axis is r /R.

Another feature which is characteristic of the cross section is r which is the radius of the circular are between two adjacent lobes. While this dimension is useful for constructing the theoretical outline of the crosssection, an easier feature for use in measurement is the distance d, which is the shortest distance between two indentations measured across the major axis of the fiber cross-section.

According to the invention, the ratio of length to width A/B of the cross-section is from 1.4 to 2.4 and the tip radius ratio r lR for the lobes on the major axis is between 0.20 and 0.45. The tip radius ratio of the lobes on the minor axis is from 0.8 to 2.1 times the tip radius ratio of the lobes on the major axis. The crosssection must be properly indented between lobes to provide the desirable properties of the invention; for this reason, the ratio d/2r is from 0.6 to 1.0.

While the above features may appear to be complicated,they are quite simple to measure on enlarged photomicrographs of cross-sectional views and the stated parameters are critical for obtaining the desirable fiber and pile fabric properties.

Each of the FIGS. 1 to 4 show cross-sectional shapes within the scope of the invention. The measurements for each of these are shown in Table l.

The precise reasons for the unusual combination of properties of the invention are not completely understood but a few general principles have emerged in the course of developing the fibers of the invention. First it is necessary to have sufficient indentations in the cross-section to permit hiding of trimer and other low molecular weight materials present in polyester fibers. When synthetic fibers are incorporated in fur-like pile fabrics, the pile fabrics are ironed and stroked very vigorously with a fur iron to remove fiber crimp thereby providing a smooth hand for the pile fabric. This ironing operation tends also to deposit the low molecular weight materials in the grooves of the fiber thereby removing it from the broad tactile surfaces of the fiber. The resulting fabric has an exceptionally smooth pleasant tactile hand.

Another-guideline of the invention is to avoid providing large areas of finger contact. For this purpose the cross-section of the filament of the invention is designed so that it does not pack closely with adjacent filaments.

The denier per filament, which is between 2 and 14, and the oblong cross-section of the fiber is important for providing fur-like fabrics with a soft feel but which still have resilience in the pile. Filaments with oblong cross-section are more satisfactory for this reason than filaments of generally round cross-section of the same denier per filament. The oblong cross-section filaments tend to bend easily in at least one direction providing a soft hand. If denier is at least 2 and no more than 14, the fur-like fabrics have soft hand and good resilience.

Filaments of the invention have a pleasant luster since they have a lobed surface. Another important feature of the invention is avoidance of fibrillation. The tip radius ratio of the lobes and the relative sizes of the major and minor lobes appear to have bearing on this quality. Polyester filaments which are too highly indented or which have thin fins along the length tend to fibrillate when passed through the fur iron, and during the life and use of the garment. The fibrillation in turn makes the garment unsatisfactory because of the matted appearance, particularly around the collar. The filaments of the invention avoid fibrillation by having a large mass at the center of the cross-section, by avoiding excessive indentation, and by requiring a tip radius ratio above 0.2 for the lobes on the major axis.

EXAMPLE I A multifilament yarn of polyethylene terephthalate continuous filaments was melt-spun at 305C. from a polymer containing 0.1% titanium dioxide having a relative viscosity of 21 determined for a solution of 80 mg. of polymer in ml. of hexafluoroisopropanol solvent at 25C. The polymer was extruded at the rate of'8.5 lbs./hr. through a spinneret having 36 clusters of diamond-shaped orifices, there being three diamondshaped holes in each cluster. The three orifices within each cluster were closely spaced to permit melt coalescence immediately after extrusion. A plan view of a single cluster is shown in FIG. 5. The length of the central diamond-shaped orifice in the cluster measured along the face of the spinneret was 0.020-inch and the width was 0.0l2-inch. The two orifices located on each side of the central orifice were 0.016-inch long and 0.009- inch wide. The three orifices in each cluster were separated a distance of 0.003-inch and were located in a straight row with their longest dimensions parallel as indicated in FIG. 5. The multifilament yarn produced from the 36-cluster spinneret was wound up at 1200 yards/minute. The wound-up yarn at this point was 530 denier with 36 filaments. (Denier per filament was 14.7.)

About 100 ends of yarn were combined to produce tow of about 53,000 denier. This tow was drawn in 90C. water to obtain tow having filaments of 4.6 denier per filament. Samples of the tow 10 inches in length had the following properties: tenacity 4.0 gpd, break elongation 31%, boil-off shrinkage 2.1%, dry heat shrinkage at 196C. 7.2%. The tow was then passed through a stuffer-box crimper. The filaments after this point had 9 crimps per inch and the denier was 4.6 per filament. The crimped tow was cut to staple 1.25 inches in length.

The drawn filaments prepared from the threediamond orifices had a scalloped oval cross-section with the following parameters: A/B 1.6; r /R 0.33;

r /r 1.34; and d/2r 0.82. The cross sections were obtained by embedding a bundle of filaments in a resin medium and cutting with a microtome. The resulting slices were observed in a microscope under an immersion oil and were then photographed and enlarged for measurement.

The staple fibers were stock-dyed at 250F. under pressure using 3 grams per liter of a modified liquid biphenyl as dye carrier and the following disperse dyes based on the fabric weight): 2.7% Latyl Bordeaux B; 3.1% Latyl Cerise N, and 0.8% Latyl Brown MS. The dyebath was drained after the temperature had cooled to F. No scouring step was employed after the dye cycle. The resulting fibers were maroon in color after tumble drying. These fibers were processed into silver.

The above dyeing conditions have been shown to leave a tacky low molecular weight material on the surface of round fibers; in the present example with fibers of scalloped oval cross section, this material was again found present. Although the same tacky material was found present as particles on the surface of filaments of this example, it did not adversely affect the aesthetic properties of fur-like fabric prepared from these filaments. To avoid a tacky feel in pile fabrics made with round fibers, it has usually been necessary to cool the bath to only about before separating fiber from bath and to scour the resulting fibers in a separate operation at close to the boiling point.

A sliver knit fabric was prepared from the above dyed staple as follows: First, the dyed staple was processed on a woolen card to produce a 125 grain sliver. The sliver was then fed to a Wildman Maxi-Pile sliver knit machine. The machine is similar in basic principle to the machine depicted in U.S. Pat. No. 3,516,265 for furs of uneven density, but in the present case furs of uniform density were prepared. Sufficient staple fiber was picked up by the machine to give a knit tubing with a total weight of 8.5 oz./linear ft. The backing yarn for this fabric was a singles yarn with a cotton count of 14 made of polyethylene terephthalate homopolymer staple wherein the polymer had a relative viscosity of 23. The filaments were 3.0 denier per filament and 2 inches in length.

Following knitting, the tubing was slit and backcoated with an acrylic resin latex, then heated to crosslink the resin and to dry. The resulting sliver-knit fabric was then finished in the following sequence: (1) sheared in two passes to 7/l6'-inch pile length; (2) passed four times under a fur iron similar to that shown in U.S. Pat. No. 3,557,415, otherwise known as an electrifier cylinder. The cylinder was maintained at 380F. The pile fabric was passed under the iron at 3% yards per minute at moderate pressure. After 4 passes, the crimps at the ends of the pile fibers were substantially removed as desired; (3) resheared and wire-brushed, 1 pass; (4) resheared without brushing; (5) ironed again at 380F., 6 passes; (6) resheared 7/ 16-inch, twice; (7) ironed at 300F. to polish, twice; and (8) sheared at 7/l6-inch, twice.

The resulting fabric had a pleasing luster and the hand of the fabric was non-tacky. The pile was soft and resilient. There was no evidence of fibrillation, i.e., no split fiber ends observed in microscopic examination of the fabric. The hand was much less tacky than for similar fabric made from round fibers. Other properties of v the fabric are shown in Table 2. It will be noted from Table 2 that the fabric contained 0.85% of an extractable material which is largely in the form of surface deposits of polyester trimer. A stereoscan photomicrograph showed that the surface deposits were primarily in the grooves of the fibers. Apparently, surface deposits in this location were not available to fingers touching the pile fabric. Pile fabrics of round fibers with similar amounts of extractables were tacky and unpleasant.

EXAMPLE II Filaments with scalloped oval cross-section were prepared from a different type of spinneret, but were otherwise prepared as in Example I. In this case the spinneret orifice consisted of 36 clusters with 3 round holes each. The 3 holes in each cluster were interconnected by channels as shown in FIG. 6. The outer holes were 0.008 inch in diameter and the large center hole was 0.0105 inch in diameter. The connecting channels were about 0.0025 inch wide and 0.004 inch long. The outer holes were each centered 0.0133-ir1ch from the center of the center hole.

The resulting filaments had a bundle tenacity of 3.3 gpd, elongation at break of 28% and boil-off shrinkage of 1.1%. The dry heat shrinkage of the uncrimped drawn tow at 196C. was 6.5%. The cross-sectional measurements for the filaments were A/B 2.04; r /R 0.33; r /r 1.64; and d/2r 0.77. After passing through the stuffer-box, the filaments had 9 crimps per inch. The filament denier was 4.7. The cut staple fibers were 1.25 inches long. The filaments were stock-dyed to produce a gray color. The dyeing conditions were otherwise the same as in Example I and no after-scour was used. The fabric was finished in a manner similar to Example I. The fabric was similar in aesthetic appeal. Properties of the fabric are shown in Table 2. The fabric had a non-tacky hand despite the presence of trimer as shown by 1.0% extractable material.

EXAMPLES IIl-VI Several different types of spinneret and melt spinning conditions were employed to make several types of filament with scalloped oval cross-section. These filaments were processed as in Examples I and II. Sliver knit fabrics were prepared. The filament cross-sectional measurements and properties of the fabrics are described in Table 3. It will be noted that all of the fibers in Table 3 except the one designated Example V produced acceptable fabrics. The fiber of Example V had a ratio of d/2r of 1.08, which is outside of the invention, and the pile fabric of Example V had a tacky hand. The pile fabrics of Examples 111, IV and VI had a non-tacky, soft and resilient hand. It was found that the fibers of Exampls III, IV and VI fibrillated less than a trilobal polyester fiber having a modification ratio (as defined in Holland US. Pat. No. 2,939,201) of 1.8 and the same denier per filament.

EXAMPLE VII Another sliver knit fabric was prepared having a pile surface composed of 50% by weight of the 3.4-denier fibers of Example 111 and 50% of 14-denier fibers of 2- inch length wherein A/B was 1.79; r /R was 0.32; r /r was 1.24; and d/2r was 0.78. The 3.4-denier fibers were dyed an off-white beige shade and the 14-denier fibers were dyed a dark brown. The fabric was knit and finished as in Examples 1 and 11, but was sheared to 11-inch pile height. The finished fabric had a pleasing luster, and a soft, resilient, non-tacky hand. The 14 dpf fibers, being longer, were more prominent at the surface of the pile, and the resulting fabric was similar in appearance to natural furs. The 14 dpf fibers served as guard hairs, being similar to the guard hairs of natural furs in appearance and in feel.

PROPERTIES OF SYNTHETIC FURS PREPARED IN EXAMPLES I AND 11 Ex. I Ex. 11

Total fabric weight, oz/yd 14.8 14.0 Shaved pile weight 10%, 6.8 6.5 oz/yd Weight of knit backing, oz/yd 8.0 7.5 Fabric thickness in finished state (after latexing). inches 0.44 0.49 Weight loss in Wyzenbeeck abrasion, after 50 cycles/after 0.47/.74 0.60/1.1O 10 X oz/yd cycles Extractable with carbon tetrachloride, by wt. of dyed 0.85 1.0 staple TABLE 3 DATA FOR PILE FIBERS 0F EXAMPLES 111 TO V1 EXAMPLES 111 IV V VI Denier per filament 3.4 3.3 3.4 2.7 A/B 1.64 1.59 1.74 1.60 n/R 0.35 0.40 0.38 0.35 r lr 1.01 1.08 1.38 1.26 d/2r 0.71 0.87 1.08 0.92

I claim:

1. A polyester filament of 2 to 14 denier having an oblong cross section, continuously along its length, characterized as follows:

a. By major and minor axes of symmetry which are perpendicular to each other;

b. By a ratio of length A to width B, measured along the axes of symmetry, of from 1.4 to 2.4;

c. By a lobe located on each extremity of the major axis which has a tip radius ratio r,/R of 0.20 to 0.45, where r, is the radius of the lobe tip and R is the radius of a circle circumscribed about the oblong cross section;

d. By a lobe located on each extremity of the minor axis which has a tip radius ratio r /R of 0.8 to 2.1 times the tip radius ratio r,/R of the lobes on the major axis;

e. By indentations between the lobes on the major and minor axes; and

f. By the shortest distance d between two indentations on opposite sides of the major axis being from 1.2 to 2.0 times the radius r, of the lobes on the major axis. 

1. A POLYESTER FILAMENT OF 2 TO 14 DENIER HAVING AN OBLONG CROSS SECTION, CONTINUOUSLY ALONG ITS LENGTH, CHARACTERIZED AS FOLLOWS: A. BY MAJOR AND MINOR AXES OF SYMMETRY WHICH ARE PERPENDICULAR TO EACH OTHER, B. BY A RATIO OF LENGTH A TO WIDTH B, MEASURED ALONG THE AXIS OF SYMMETRY, OF FROM 1.4 TO 2.4, C. BY A LOBE LOCATED ON EACH EXTREMITY OF THE MAJOR AXIS WHICH HAS A TIP RADIUS RATIO R1/R OF 0.20 TO 0.45, WHERE R1 IS THE RADIUS OF THE LOBE TIP AND R IS THE RADIUS OF A CIRCLE CIRCUMSCRIBED ABOUT THE CROSS SECTION, D. BY A LOBE LOCATED ON EACH EXTREMITY OF THE MINOR AXIS WHICH HAS A TIP RADIUS RATIO R2/R OF 0.8 TO 2.1 TIMES THE TIP RADIUS RATIO R1/R OF TE LOBES ON THE MAJOR ACIS, E. BY INDENTATIONS BETWEEN THE LOBES ON THE MAJOR AND MINOR AXES, AND F. BY THE SHORTEST DISTANCE D BETWEEN TWO INDENTATIONS ON OPPOSITE SIDES OF THE MAJOR AXIS BEING FROM 1.2 TO 2.0 TIES THE RADIUS R1 OF THE LOBES ON THE MAJOR AXIS, 